The Extension And Validation Of The Msr System Code,TREND

Molten Salt Reactor,one of the six advanced reactor types of the fourth generation nuclear energy system,is famous for its following features: the boiling point of the molten salt is as high as 1300?,which leads to a high operating temperature and a high efficiency of the system.Besides,a high heat capacity leads to a high enegy density system.Furthermore,MSR owns a lowe operation pressures(?0.1MP),which will improve the the inherent safety of the system especially for the LOCA accident.In 2011,Chinese Academy of Sciences(CAS)launched the Thorium-base Molten Salt Reactor(TMSR)nuclear system project,aiming to develop thorium-fuled molten salt reactors.MSR research started at Oak Ridge National Laboratory(ORNL)when the Aircraft Reactor Experiment and the Molten Salt Reactor Experiment(MSRE)was constructed in the 1960s.After decades of development,the MSR concept led to two major types of MSRs.The first is the Fluoride-salt-cooled High temperature Reactors(FHR)with solid fuel elements and molten salt as the coolant.In the second subclass,the liquid-fuel MSR adopte the graphite as moderator,a large number of graphite form the fuel channels.Different from the solid fueled reactor,the fissile material is dissolved in the molten salt as both the fuel and coolant,leading to a much more unique and complicated system.Besides,DNP will drift with the flowing salt in the MSR,which leads to a non-negligible loss and variation of reactivity especially during transients.Therefore,the system analysis codes for the solid fueled reactor such as RELAP5,are not suitable for the liquid-fuel MSR.Considering the characteristics of MSR,the Shanghai Institute of Applied Physics(SINAP)developed the TREND code for analyzing the systemic analysis and safety feature of MSRs.In this paper,the model is extended and verified based on the TREND code for its application on TMSR-LF1,and a system code suitable for transient analysis of liquid molten salt reactor system is formed.The main research content of this paper includes:1)TREND code is extended to be suitable for the liquid fueled MSR.A new neutron dynamic model was developed which was based on the solution of one-dimensional two-group neutron diffusion equation coupled with the 1D equation for delayed-neutron precursors.Also,2-D heat conduction model was also extended in the code.And the branch model was added to the code,based on which the parallel multi-channels can be solved.2)The correctness of the model and the extended code is verified following contents: detailed code-to-code comparison with established thermal-hydraulic system codes such as RELAP5 and fluent.Also,the experiment of the CIET was verified to verify the thermal steady-state and transient computing ability of the TREND code.As for the neutron model,the The correctness of the model was validated with the experimental data from pump start-up,the pump coast-down,the natural circulation and the reactivity perturbation transients of the Molten Salt Reactor Experiment(MSRE)at Oak Ridge National Laboratory(ORNL).The calculation results of each module and the coupling calculation results among each module all indicate the correctness of the TREND code.3)In order to further verify the applicability of the TREND code in the transient analysis of MSR,disturbance cases and the reactivity insertions cases are simulated to analyze the operational performance based on a three-loop model of 10 MW MSR.4)At the same time,the experiment of the passive residual heat removal system of SF0 facility was carried out.Based on the experimental data,a passive residual heat removal system model of the TREND code was developed,in which 2-D heat conduction model and Radiation heat transfer model was planted.The deviation between the calculation results of the code and the experiment was about 10%,which was in good agreement.All of these will provide reference for the heat removal capacity of passive residual heat removal system of TMSR-LF1 in the future.5)The transient behavior of the HTS test loop was analyzed based on the experimental data and TREND code.Three disturbed transient experiment were carried out,inlcued the power step change,change of the salt mass flow rate and the power sinusoidal variation.The results bettew the experiment and the TREND code were in good agreement,which provide a certain basis for the transient behavior analysis of high-temperature molten salt loop with TREND code.